Physical
characteristics: a semiprecious
stone that is usually rich azure blue and is essentially a complex
silicate
often with spangles of iron pyrites.
Physical
characteristics: tektite
(green and glossy) from River Valley in Czech Republic; known also as
Vltava.
Moonstone
Physical
characteristics: a transparent
or translucent feldspar of pearly or opaline luster.
Obsidian
Physical
characteristics: volcanic
bright and vitreous lustrous glass.
Onyx
Physical
characteristics: translucent
chalcedony in parallel layers of different colors.
Opal
Physical
characteristics: a mineral
that is a hydrated amorphous silica softer and less dense than quartz
and
typically with definite and often marked iridescent play of colors.
